czsky/en/constellation/ursa minor.md

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Ursa Minor skybber 2021-08-01 07:46:36.252401 skybber 2022-02-14 14:42:38.045337

A small constellation in the northern sky with the north pole less than one degree from Polaris. In this direction, the elongated axis of our planet is lost in the depths of space, and therefore the stars around the celestial pole can always be found in clear skies, because they are Circumpolar in our area. The constellation of the Ursa Minor itself is relatively inconspicuous and consists mainly of an outline consisting of seven stars, often called the Little Dipper. The two stars, Kochab and Pherkad, which form its rear wheels, are called the guardians of the pole. As the stars of the Little Dipper are mostly between the 2nd and 5th magnitude in brightness, and the constellation is always above the horizon at a greater or lesser height in the northern hemisphere, it may be used as a rough aid to ascertain the state of clearness of the sky. Indeed, if the stars δ, ε and ζ of Ursa Minor are not visible, the atmosphere is so opaque that we may not even identify the basic shape of the constellation. If the star η Umi (4.9mag) is not visible, conditions are too poor for serious observation of deep-sky objects. On the other hand, if it is visible from the suburbs or illuminated locations, then the atmospheric clarity is very good. From the countryside it should not be a problem to see even θ (5.2mag) and 19 Umi (5.5mag) on any average night. There are otherwise few interesting objects in the constellation. The most important of these is Polaris, the North Star, because of its proximity to the north celestial pole.

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In dark skies, try to make your way to Polaris in the form of a 40-degree complex of physically related dark nebulae (called the Ling filament or Polaris loop). However, you need to start tracking it just northeast of Deneb, where the very dark Le Gentil 3 region is located. It clearly cuts into the Milky Way just off North America and transitions smoothly into its surroundings to the east. The complex then stretches west to the pair of stars α and β Cephei at the very edge of the Milky Way and extends further north to γ Cephei, where it loses much of its contrast due to the poorer stellar field. Leaving the Milky Way, the complex can be seen as a dark band in the sparse star field where it splits about five degrees north of the reflection nebula NGC 7023, in a star-poor spot about 6 by 4 degrees in size. One branch continues towards the pole (the area around Polaris itself is visually quite deficient in stars within a radius of 2-3 degrees), the other goes in the direction of a nameless fifth-magnitude star, where it fades out. Yes, there are indeed dark nebulae in the Little Dipper! Of course, the dark complex is not at all conspicuous and stands out the better the fainter stars are seen at the observing site. A similar dark serpentine extends towards Polaris from the eastern part of Cassiopeia, north of the double cluster h / χ Perseus. However, it is narrower, straighter and even less conspicuous. Observing dark nebulae is really fascinating, especially if you don't need any binoculars!